Currently, a promising area is the development of technologies for sintering or briquetting of converter sludge. Recycling of this sludge into production will allow solving a number of important tasks for modern metallurgy in the utilization of man-made waste, saving raw materials and reducing the cost of steel. The efficiency of utilizing useful components in the composition of briquettes is significantly higher than in any other state (in a fine or polydisperse fraction, in sorted form). In this paper, we consider the development and justification of an integrated approach to thermochemical sintering of converter sludge based on conditioning of iron-containing sludge by non-thermal adsorption dehydration and thermochemical sintering with simultaneous reduction of iron from oxides. Adsorption dehydration to a moisture content of 2 – 3 % is provided by a short-term contact of iron-containing slimes with a porous energy carrier, brown coal semi-coke, which is separated by pneumoseparation and sent for energy technological use, and the iron-containing product mixed with coals is subjected to thermo-oxidative coking. Coking is carried out in an annular furnace with a rotating hearth, where, when temperatures reach 1050 – 1100 °C, a large and durable lump material is formed with 55 – 60 % of the iron-containing product with almost complete reduction. Thermodynamic modeling of converter sludge sintering with coals was carried out. A tool for performing computational experiments using methods of thermodynamic modeling of the studied object was the Terra software package designed to calculate the thermodynamic properties and composition of the phases of equilibrium state of arbitrary systems with chemical and phase transformations. The results of thermodynamic modeling were fully confirmed by the experimental studies. The obtained material is an analog of ferrocox containing 35 – 39 % of iron and 45 – 49 % of carbon, while the zinc oxide content does not exceed 0.017 %.

The article considers the features and characteristics of spreading of neutral gas jets in the gas-dynamic section before interaction with the slag melt, which is further inflated to apply a refractory skull to the unit lining. The flow of a supersonic jet into the working space of the converter after tapping has the wave structure. The model for calculation of attached mass of the surrounding gas located in the converter working space is considered. The problem statement considers the known data on gas dynamics during the formation and flow of the jet, which affect the efficiency of turbulent transfer in the boundary layer. The calculation scheme is based on the hypothesis of existence of an initial boundary through which a chemically active gas from the environment penetrates into the gas jet, and the shape of the limit boundary is assumed to be cylindrical with a radius equal to the maximum radius of the first barrel of the non-calculated jet. Numerical calculations make it possible to determine the average mass velocity and temperature in an arbitrary section of a supersonic non-calculated jet before its introduction into the slag melt. The authors describe the influence of the relative temperature θ, nitrogen temperature in front of the nozzle T 0 during spreading of the jet in the converter cavity, and nitrogen flow through the nozzles V n on value of the attached mass q , the averaged values of velocity and temperature W x and T x in an arbitrary cross-section of a supersonic non-calculated jet in the gas dynamic section. The information obtained can be used in the development of gas-powder purging systems in aggregates and steel ladles, shotcrete systems and the supply of neutral gas jets when replacing oxygen flows during purging and using two-tier tuyeres.

On the basis of a complex of researches carried out in laboratory and industrial conditions using standard methods of metallographic analysis and impact testing of balls, the regularities of the formation of the quality of the macro- and microstructure of grinding balls in relation to their operational resistance in the production of rail steels and specialized ball steels of various chemical compositions are determined. When studying samples of five different compositions, it was determined that grinding balls made of 76XF steel have an optimal homogeneous microstructure that provides high impact resistance in combination with increased hardness after heat treatment. Additional alloying of the specified rail steel with chromium and nickel in excess of the requirements of regulatory documentation leads to the formation of dendritic liquation in the cast structure, which decreases, but is not completely eliminated after heat treatment of the produced balls. This microstructure is defective and causes a reduced impact resistance of grinding balls. In the production of balls made of 90HAF grade hypereutectoid rail steel, cementite is present in the microstructure, which reduces the balls' resistance to shock loads; at the same time, there is no noticeable increase in the hardness of heat-treated balls compared to balls made of 76XF steel. With regard to balls made of specialized steels of grades Sh2.1 and Sh2.3, the determining effect on their impact resistance of macrostructure defects passing from the initial cast blanks has been established. The features of the quenching microstruc-ture of grinding balls made of specialized steels of the specified grades, formed by varying the modes of their heat treatment, does not significantly affect the impact resistance of the balls

On the basis of metallographic studies, the authors determined the characteristic defects of grinding balls rolled from the rejects of continuously cast billets of K76F rail steel. Relationship of the presence of internal defects of the balls with their impact resistance was established. Defects in the form of internal cracks with accumulations of non-metallic inclusions in the area of their localization and flocks have the greatest impact on the reduction of balls impact resistance. Such defects are the cause of balls destruction during impact resistance tests in 62 and 17 % of cases, respectively. The effect of internal cracks without significant accumulations of non-metallic inclusions and quenching microcracks located along the boundaries of the phase interface was estimated at 12 and 9 %. The regularities and mechanism of influence of the rejects chemical composition of K76F rail steel billets on the probability of destruction of the balls produced from them during impact resistance tests were established. An increase in sulfur content in the billets of the studied rail steel reduces impact resistance of the balls produced from them, as it contributes to formation of non-plastic sulfides that concentrate in the area of internal cracks. An increase in hydrogen content in rail steel naturally contributes to an increase in probability of formation of the flocks, which significantly reduce the balls stability to shock loads. An increase in carbon content in the initial billets affects the increase in probability of destruction of K76F steel balls during copra tests. It is explained by formation of cementite-type carbides when carbon content corresponding to the eutectoid steel is reached. In general, the relative degree of influence of the K76F rail steel chemical composition on impact resistance of grinding balls is 48 %.

Technological features of powdered reagents injection into the melt using a submersible tuyere were investigated for the research and development of the main provisions of rail steel out–of-furnace treatment in a ladle-furnace. Authors analyzed the characteristics of influence of a directed heat flow through the tuyere conditional separation wall from metal to two-phase gas-powder flow under purging conditions. Using numerical methods, we determined the parameters of influence of the submersible tuyere surface temperature on characteristics of the transporting gas, concentration of the powder and its density, and on characteristics of the gas-powder flow, including the aerodynamic drag coefficient, pressure of the transporting gas, difference in phase velocities, equivalent diameter, and particle shape coefficient. The obtained experimental results show that, at fixed flow rate of the transporting gas, more significant heat flows are created by using a lighter gas (nitrogen) ensuring stable operation of the blowing device, while the diameter of powdered particles does not affect the amount of heat transferred from the tuyere wall to the transporting gas. It was established that, when using submersible tuyeres and heating the gas–powder flow to a temperature of 500–600°C, the strength of the interfacial interaction changes by 2 to 10 times depending on the particle shape coefficient, concentration of the injected powder, pressure of the transporting gas, difference in phase velocities, and the powder density.

Prediction and control of the carbon content after the end of oxygen blow in BOF converter are key points of steel production efficiency. One of the most accurate methods is the dynamic predicting method based on the use of intermediate sublance measurement (TSC probe) when about 85 – 90 % of total oxygen is consumed and on the final period model. Models of the final period are traditionally based on exponential or cubic functions, currently there are developments based on neural network technologies. We investigated the possibility of using a neural network to predict the final carbon content using the results of intermediate sublance measurement (TSO probe) when about 95 % of total oxygen is consumed. As a model of the final period, a two-layer neural network with one hidden layer and an activation function of the Softplus type for all neurons was implemented in software. The input vectors contain initial carbon content and oxygen consumption for the second blow values. The output vector contains the predicted final carbon content, the output training vector - actual final carbon content values. The network was trained on 700 heats data of the training set. The model trained in this way was tested on 232 heats data of the testing set. The prediction errors distribution and values of the mean absolute error and root mean square error for the training and testing sets are correspondingly close. They are also comparable with similar indicators of the heats, the final period of which was carried out without oxygen blow (only flux additions and/or nitrogen blow), and this indicates a high accuracy of the prediction.

Application of the iron-containing wastes, such as converter production sludge, iron-containing concentrates, mill scale, iron ore-dressing wastes, etc., is one of the promising areas in metallurgy. Development of new resource-saving technologies with application of those waste requires preliminary research and accumulation of the information on the iron reduction. The present work considers the processes of iron reduction under the various conditions. We engaged the thermodynamic simulation method based on search for the entropy maximum. The “Terra” software package (Bauman Moscow State Technical University) is the thermodynamic simulation tool. The “Terra” complex is designed to calculate thermodynamic properties and composition of the phases in the arbitrary system with chemical and phase transformations in the equilibrium state. With this software package, we investigate the iron disoxidation processes by various reduction agents (carbon, manganese, and silicon) in the model thermodynamic systems, and determine the optimal conditions for the temperature and the reducing agent consumption. The paper presents the results on the processes in the equilibrium metal–slag system. We analyzed the equilibrium state of the metal-slag system within the temperature range of 1773–1973 K under the different slag amounts; determined the domains of the oxidation–reduction processes; and assessed the influence of the metal components on the iron oxide reduction from slag to metal. Temperature dependences of the equilibrium system composition are obtained for various metal-to-slag ratios and the optimal conditions for the iron reduction are determined.

The theoretical substantiation was carried out for increasing the efficiency of converter gases afterburning in the unit with a two­tier supply of multi­pulse oxygen jets and combustion of CO to CO2 in the channel flow of gases leaving the reaction zone. The authors made the thermodynamic analysis of the process of exhaust gases afterburning in converter cavity when using two­tier oxygen lances for refining. It is shown that when oxygen gas jets are blown through the upper­tier nozzles with a flow rate of 10 – 40 % of the total minute flow rate, a sufficiently complete afterburning of carbon monoxide CO is not provided. The limiting factors are the uneven amount and disorganized output of the CO formed in the reaction zones during various operation periods, low efficiency of mixing the waste stream with high­speed gas jets and an excessively excessive amount of oxygen supplied for afterburning, insufficient mixing of the components of the gas phase and low reaction rate. It is shown that when the conditions are provided for CO afterburning to the concentration ratio in the gas phase, temperature of the exhaust gas in the converter cavity can increase from 1800 to 2000 K, then the thermal effect of the exothermic reaction decreases. The amount of oxygen injected for CO afterburning must correspond to the residual carbon content in the metal at m3/min ≈ 100 [Сост ] %. Excess of oxygen in the gas phase and presence of a significant amount of neutral gas significantly reduce the utilization rate of the generated heat in the unit.

In this work, the decarburization of periclase-carbon and aluminum-periclase-carbon ladle refractories has been studied. The decarburization processes take place already at the stage of drying and heating of the lining after repair, during its heat treatment using gas or electric stands. These processes cause irreparable damage to refractories even before the ladle is put into service (before contact with molten steel). One of the ways to increase the oxidation resistance of carbon-containing refractories is a use of antioxidants (Al, SiC, Si, etc.), which are introduced into the composition of a raw mixture at the stage of manufacturing. The action of antioxidants is based on the priority oxidation compared to carbon. Antioxidants act in a certain temperature range, which opens up wide opportunities for the development of energy- and resource-saving temperature conditions for lining heat treatment. The thermogravimetric analysis was carried out for AMC 78-8/7HG, RI-MC175LC (RI firm) and MayCarb 284-AX (MAYERTON) periclase-carbon and aluminum-periclase-carbon unfired resin-bonded refractories used in the production of working layers of steel-pouring ladle linings. The thermogravimetric analysis of refractory samples was carried out using a LABSYS evo TG DTA DSC 1600 derivatograph with heating to a temperature of 1100°C at a rate of 15°C/min. X-ray phase analysis was performed using an XRD-6000 X-ray diffractometer. The results of thermogravimetric analysis are presented in the form of derivatograms. It has been found that the maximum rate of carbon oxidation in all the cases is obtained at a temperature of 700–750°C. Therefore, to implement the low-decarburization first heating of a ladle after repairing, the temperature modes that include low-temperature (up to 500°C) holdings of the lining are recommended for refractories of the studied types.

The article describes theoretical and experimental studies of dependence of viscosity, coefficients of sulfur and boron distribution between slag and metal, and wear degree of periclase-carbon refractories on basicity and boron oxide content in slag. It is shown that formed slags have basicity of 2.0 – 5.0 and rather high liquid mobility. These slags are characterized by an equilibrium interfacial distribution coefficient of sulfur increased to 5 – 20, which provides equilibrium sulfur content in the metal reduced to 0.001 – 0.005 %. The results of fundamental studies of the physicochemical properties of refining slags of СаО – SiO2 – В2O3 – Al2O3 – MgO system formed the basis for development of the composition of environmentally friendly fluorine-free ladle slags and technological methods for their formation in ladle-furnace unit. The recommended composition of such slags of low viscosity, which allows deep metal desulfurization, direct steel microalloying with boron and low aggressive effect on periclase-carbon refractories, provides formation of slags with a basicity of 3.0 – 4.0, containing 1 – 4 % B2O3 , 15 % Al2O3 and 8 % MgO. The formation of environmentally friendly ladle slags of the recommended composition was carried out in a ladle-furnace by loading lime, boron-containing material – colemanite (Turkey) containing 39 – 41 % B2O3 , 26 – 28 % CaO, not more than 5 % SiO2 and 3 % MgO, and pyramidal aluminum into the steel-teeming ladle for slag deoxidation and boron recovery. Introduction of the developed technology for the formation of ladle slags of recommended composition ensured the production of economically alloyed low-carbon structural boron-containing steels with a low sulfur content, incl. for large diameter pipes with high strength properties.

Abstract—We perform a theoretical substantiation of the efficiency increase of the converter gas afterburning in the installation supplying two-tier, different impulse oxygen jets, with CO combustion to CO2 in the channel gas flow leaving the reaction zone. We analyze the thermodynamics of the exhaust gases afterburning process in the converter bath when using (for the blowing) the two-tier oxygen lances. When the oxygen gas jets are blown through the nozzles of the upper tier with the flow rate of 10–40% of the total minute consumption, then sufficiently complete afterburning of the carbon monoxide, CO, is not provided. The uneven amount and unorganized output of the CO formed in the reaction zones during the operation, low efficiency of the exhaust stream mixing with the high-velocity gas jets and the far excessive oxygen amount supplied for the afterburning, insufficient mixing of the gas phase components, and low reaction rate are the limiting factors. We show that at providing conditions for the CO afterburning to the $$\frac{{{{P}_{{{\text{C}}{{{\text{O}}}_{{\text{2}}}}}}}}}{{{{P}_{{{\text{CO}}}}}}}$$ = 1 ratio of concentration in the gas phase, the exhaust gas temperature in the converter bath might increase from 1800 to 2000 K; furthermore, the thermal effect of the exothermic reaction decreases. The oxygen amount injected for the CO afterburning should respect to the residual carbon content in the metal under the condition of $$V_{{{{{\text{O}}}_{2}}}}^{{{\text{add}}}}$$ , m3/min ≈ 100[Cres]%. The oxygen excess in the gas phase and significant amount of the neutral gas reduce essentially the coefficient of utilization of the heat released in the facility.

Based on the state diagrams of two–component silicate systems SrO – SiO 2 , BaO – SiO 2 , CaO – SiO 2 , the authors have determined the activity of components in invariant (eutectic and monotectic) points of the systems under consideration. Crystallization processes at invariant eutectic points l 1 and l 2 are considered as chemical reactions l e 1 ( K SiO 2 (l) + lMe O(l)) → C SiO 2 (sol) + α( Me O·SiO 2 )(sol), l e 2 ( m SiO 2 (l) + nMe O(l)) → ( Me O·SiO 2 )(sol) + b (2 Me O·SiO 2 )(sol), for which the values Δ G ° T and the equilibrium constants were established. The values of a Me O in the slags were determined at given temperatures and known values of the component activities in metal melts in equilibrium with slag. In homogeneous slag melts, the activity of alkaline-earth metal (AEM) oxides was defined from the constants of equilibrium reactions of reduction of these metals from slags by silicon of iron-silicon metal melts. In the zone of homogeneous slag melts, the dependences a SiO2 = f ( x (SiO2 ) ) were constructed at temperatures of 1600 and 1700 °C, and when using data on the activities of AEM (Sr, Ba, Ca) in metallic high-silicon melts, the dependences lg a (SrO) = f ( x (SiO2 ) , x (Si) ) at 1493 °C and lg a (BaO) = f ( x (SiO2 ) , x (Si) ) at 1450 °C were determined. On a three-parameter diagram in coordinates a [Si] – a (SiO2 ) – a ( Me O) (for AEM), the dependencies a (SrO) = f ( a [Si] , a (SiO2 ) ) at 1493 °C and a (BaO) = f ( a [Si] , a (SiO2 ) ) at 1450 °C were constructed. It is shown that low equilibrium values of a (SrO) and a (BaO) , lg a (SrO) = f ( a (SiO2 ) , a [Si] ) ≤ (–4) and lg a (BaO) = f ( a (SiO2 ) , a [Si] ) ≤ (–3), can be achieved at equilibrium values of silicon activity in metal melts a [Si] > 0,5 during strontium reduction and a [Si] > 0,7 during barium reduction.

The article focuses on the study of the nature of dust and smoke generation in the gas-oxygen blowing of a converter bath. The main causes of metal waste are determined. The influence of the main parameters of the process on the loss of metal at the dust discharge and evaporation of iron in the reaction zone are studied. The metal pulverization due to floating CO bubbles is evaluated. This pulverization is determined by the rate at which they rise to the bath surface. The characteristic features of the temperature regime of the reaction zone and the heat balance upon the addition of fuel to the oxygen flow are determined. The addition of fuel to oxygen makes it possible to increase the heat input into the bath, while reducing the rate of decarburization. This favors the reduction in the amount of discharged dust formed at the rupture and crushing of metal films by gas bubbles. The influence of using combustion product oxygen on the oxidation of metal impurities is considered. The blowing of carbon and alloyed steel for mill rollers is used as an example to show that the main qualities of gas-oxygen blowing are the decomposition degrees of CO2 and H2O in the bath. These indicators determine the oxidizing and heating properties of the air blast. The change in the total, consumed heat and its losses with exhaust gases are evaluated, depending on the degree, to which the oxygen flow is diluted with natural gas (methane). In these conditions, the use of submersible combustion torches with the change in their oxidizing ability makes it possible to solve various process tasks, including the provision of an efficient procedure of reducing dust emission in the converter process.

In modern ferrous metallurgy, direct reduction of iron from iron ore materials is becoming increasingly common. In order to assess the feasibility of using a particular technology, it is necessary to obtain information on the reduction processes of iron oxides. Taking into consideration that experimental research is usually expensive, a computational experiment is optimal, which allows to draw conclusions about the behavior of the studied objects on the basis of modeling high-temperature processes in complex thermodynamic systems with physicochemical transformations under equilibrium and non-equilibrium conditions. As a modeling tool, the Terra software complex created at the Moscow State Technical University named after N. E. Bauman was used. As a result of thermodynamic studies boundaries of redox processes are identified and optimal temperature and consumption of reducing agent were determined, which provide maximum degree of iron reduction. The results of simulation of iron reduction process from iron ore concentrate obtained during concentration of iron ore of Bapy deposit, by coal of Karazhyra deposit (Kazakhstan) are presented. Dependencies of composition and volume of gas phase, formed as a result of volatile coal components emission in the process of heating, degree of iron reduction at various coal consumption rates on the temperature was established. It was found that the complete reduction of iron occurs at a coal consumption of 25 kg/100 kg of concentrate and a temperature of 1013 K, and the further increase in the consumption of the reducing agent leads only to a change in the ratio of CO and SO 2 in the gas phase towards a decrease in the oxidative potential and an increase in the temperature of completion of the reducing process.

One of the promising directions in metallurgy is the use of iron-containing waste, such as converter production sludge, iron-containing concentrates, rolling scale, iron ore processing waste and others. Development of new resource-saving technologies using such waste requires preliminary research and accumulation of information in the field of iron recovery. The paper considers the processes of iron recovery from oxides under various conditions. The authors used the method of thermodynamic modeling based on the search for the entropy maximum. The thermodynamic modeling tool was TERRA software package created at the Bauman Moscow State Technical University. TERRA complex is designed to calculate the thermodynamic properties and composition of the phases of equilibrium state of arbitrary systems with chemical and phase transformations. Using this software package, studies of the processes of iron recovery by various reducing agents (carbon, manganese, and silicon) in model thermodynamic systems were carried out, and optimal conditions for temperature and consumption of reducing agents were determined. The paper presents the results of a study of processes in the metal-slag system in equilibrium. The analysis of the metal-slag system equilibrium state was carried out for the temperature range of 1773 - 1973 K with different amounts of slag. Boundaries of the areas of redox processes were determined and the influence of metal components on conditions for iron oxides recovery from slag to metal was evaluated. The dependences of the system equilibrium composition on temperature at different ratios of metal and slag were obtained, as well as the optimal conditions for iron recovery.

Abstract The coatings of Ti-Ta-N system have been obtained for the first time. Production of bioinert coatings of Ti-Ta-N system was realized by means of promising technique of electroexplosion spraying and subsequent electron-ion-plasma modification with nitrogen ions. Titanium of VT6 grade was used as a substrate for spraying of coatings. Electroexplosion spraying with use of tantalum foil leads to formation of tantalum coating on titanium substrate. Subsequent electron-ion-plasma modification with nitrogen ions results in synthesis of the following phases: TiN, Ta and β-Ti. Average microhardness values of the coatings formed vary from 449 kgf/mm2 (E = 11.47 %) to 530 kgf/mm2 (E = 10.02 %). Electroexplosion processing promotes the increase in titanium substrate microhardness near coating – substrate interface. In volume of titanium substrate the microhardness decreases to values corresponding to reference data. Irradiation of electroexplosive tantalum coating by electron beam with subsequent nitriding leads to homogenization of structure. Optimum mode of irradiation should be considered the one at powder density of electron beam of 0.5 MW/cm2. At lower value of power density the electron beam melts the electroexplosion coating to insufficient depth. At higher values of power density the electron beam leads to boiling of the melted coating and formation of larger quantities of pores. These phenomena are caused by thermal and physical characteristics of titanium substrate.

Abstract The article discusses the issues of modeling the processes of interaction of gas jets and metal melt during blowing of a converter bath. The authors developed and implemented using the finite element method a mathematical model based on a direct numerical solution of the Navier-Stokes equation without using a turbulence model. This model helped to study the dynamics of the velocity field and the boundary of the penetration of the jet into the metal. According to the results of mathematical modeling, a mechanism for the formation of carbon monoxide bubbles is suggested.

The results of basic studies of the physicochemical properties of slags are used as the basis for developing the rational composition of main magnesian slags and the process techniques for their formation by the periods of blowing a basic oxygen furnace (BOF) bath and the periods of smelting in electric arc furnaces (EAFs). The record-breaking durability of furnace linings is ensured by implementing, in the furnace shop of OJSC EVRAZ NTMK, the developed set of process techniques of forming magnesian slags in the main period of blowing and a wear-resistant skull based on the final magnesian slags. These slags produce a low aggressive effect on the lining of furnaces, while maintaining high refining properties. The furnaces’ lining durability exceeds 7000 heats; that said, the high process and key performance indicators of the process are maintained. The treatment of low manganese cast irons in the 350-ton heavy furnaces of OJSC EVRAZ ZSMK under magnesian slags allows studying the features of slag formation and changes in the chemical composition of the slag by the BOF bath blowing periods. In the course of treating phosphorous cast irons in the 300-ton BOFs at JSC ArcelorMittal Temirtau, a set of process techniques is developed for forming the magnesian slags of the recommended chemical composition by the periods of phosphorus cast iron blowing and wear-resistant skulls based on moderate-basicity final magnesian slags. The implementation of the developed process techniques ensures the lining stability of BOFs for more than 5000 heatings while maintaining the high process parameters and key performance indicators of the phosphorous treatment phase. The technology of forming rationally composed magnesian slags by the periods of smelting in EAF-135 is developed in the EAF shop of PJSC Seversky Pipe Plant. The adoption of the technology ensures the record-breaking resistance of the refractory lining of the furnace for up to 1900 heats per campaign and the high process parameters and key performance indicators of the process.

Today, in the manufacture of long-length rail strings, the obligatory heat treatment is provided after the flash butt welding operation. The basis for this operation is the unsatisfactory mechanical properties of the rail joints immediately after welding. Welding heat cycles at pulsed reflow do not always allow a welded joint with a sufficient level of ductility to be obtained. In this case, the induction heat treatment used at rail welding enterprises in Russia increases the length of the heat-affected zone, which adversely affects the wear resistance of the rails during operation. This paper presents studies in industrial conditions that were previously conducted in laboratory conditions. Studies show the possibility of obtaining the necessary mechanical properties by controlling welding heat cycles without the use of induction heat treatment.